a) Field of the Invention
The present invention is concerned with antiviral and anticancer activities of interleukin-8 (IL-8) and its use as a therapeutic agent in viral infections caused by human and animal viruses and in cancers caused by oncogene viruses.
b) Description of Prior Art
Many important infectious diseases afflicting mankind are caused by viruses of which some are frequently fatal; among such are rabies, smallpox, poliomyelitis, hepatitis, yellow fever, immune deficiencies and various encephalitic diseases. Others are significant in that they are highly contagious and create acute discomfort such as influenza, measles, mumps and chickenpox, as well as respiratory-gastrointestinal disorders. Others such as rubella and cytomegalovirus can cause congenital abnormalities; finally, there are viruses, known as oncoviruses, that can cause tumors and cancer in humans and animals.
Among viruses, the family of Herpesviridae is of great interest. Herpes viruses are highly disseminated in nature and highly pathogenic for man. For example, Epstein-Barr virus (EBV) is known to cause infectious mononucleosis in late childhood or adolescence or in young adults. The hallmarks of acute infectious mononucleosis are sore throat, fever, headache, lymphadenopathy, enlarged tonsils and atypical, dividing lymphocytes in the peripheral blood. Other manifestations frequently include mild hepatitis, splenomegaly and cerebritis. EBV is also associated with two forms of cancer: Burkitt's lymphoma (BL) and the nasopharyngeal carcinoma (NPC). In endemic areas of equatorial Africa, BL is the most common childhood malignancy, accounting for approximately 80% of cancers in children. While moderately observed in North American Caucasians, NPC is one of the most common cancers in Southern China with age incidence of 25 to 55 years. EBV, like the cytomegalovirus, is also associated with post-transplant lymphoproliferative disease, which is a potentially fatal complication of chronic immunosuppression following solid organ or bone marrow transplantation.
Another herpes virus, namely Herpes Simplex type 1 (HSV-1) is implicated as the etiologic agent of gingivostomatitis. Manifestations are fever, sore throat, and ulcerative and vesicular lesions in the mouth. The most severe clinical state caused by HSV is the primary genital herpetic infection. While HSV-1 can cause genital herpetic infection, HSV-2 is the main virus associated with this disease. This HSV infection is accompanied by vesicles, pustules and ulcers causing lesions on genital parts. A urinary retention syndrome may also be encountered. More than 80% of people are seropositive to HSV-1 or HSV-2 and studies have indicated a frequency of recurrence or viral reactivation as high as 60%. Other diseases are also associated with HSV including skin and eye infections, for example, chorioretinitis or keratoconjunctivitis. Approximately 300,000 cases of HSV infections of the eye are diagnosed yearly in the United States of America.
Human Herpes virus-6 (HHV-6) has a marked tropism for cells of the immune system and therefore, HHV-6 infection may result in alteration of the immune response. It is now clear that HHV-6 is the cause of exanthem subitum as a primary infection in children. Recent studies indicate that a significant proportion of organ transplant recipients who are seropositive before transplantation, demonstrate serologic evidence of reactivation subsequent to immunosuppression. Heterophil-negative mononucleosis-like illness and non-A, non-B hepatitis also have been associated with active HHV-6 infection. HHV-6 has often been isolated from patients with human immunodeficiency virus (HIV-1) infections. The fact that HIV and HHV-6 can reside in the same target cell has led to speculation that HHV-6 infection may act as a cofactor in the progression of HIV-seropositive patients to symptomatic AIDS. Recent studies also suggest that a human herpes virus is closely associated with HIV diseases. In fact, Kaposi sarcoma (KS), a neoplasm occurring mainly in HIV-infected person, was found to have an infectious etiology. While the virus has been named KS-associated herpesvirus, its formal classification is likely to be HHV-8.
In all infectious diseases, the efficacy of therapy often depends on host immune response. This is particularly true for herpes viruses; indeed, the ability of all herpes viruses to establish latent infections results in an extremely high incidence of reactivated infection in immunocompromised patients. In renal transplant recipients, 40% to 70% reactivate latent HSV infections, and 80% to 100% reactivate CMV infections. Such viral reactivations have also been observed in HIV-positive patients (AIDS).
Today, the number of therapeutic agents available for the treatment of viral infections remains relatively limited. For example, four major compounds are mainly used in the treatment of herpes virus infections: idoxuridine, vidarabine, acyclovir and ganciclovir. Their efficacy is limited and they cause many side effects. Allergic effects have been reported in 35% of patients treated with idoxuridine which is used only to treat HSV infection of the eye. The most common side effects of vidarabine are gastrointestinal disturbances (15% of patients). The major side effect of acyclovir is the alteration of renal function; and because acyclovir is a nucleoside analog that can be incorporated in both viral and the host cell DNA, normal division of the host cell can be affected. Regarding ganciclovir, the most important side effects are neutropenia and thrombocytopenia that occur in about 40% of AIDS patients.
Thus, there is an urgent need for the development of efficacious therapy for the treatment of viral infections.
The accumulation of leukocytes in diseased tissues is recognized as a hallmark of the inflammatory process. Recruitment of leukocytes at inflammatory sites is triggered by the local production of chemotactic cytokines. Proteins that exhibit such properties have been classified in two subfamilies according to the position of the first two cysteines, which either are separated by one amino acid (CXC proteins) or are adjacent (CC proteins). The members of the two subfamilies differ in their target cell selectivity and the chromosomal location of their genes (review by Baggiolini, et al., Adv. Immunol. 55: 97, 1994). Among the chemotactic cytokines, interleukin-8 (IL-8), which belongs to the CXC family, was originally identified in the culture supernatants of stimulated human blood monocytes. IL-8 is a nonglycosylated protein synthesized as a precursor of 99 amino acids and secreted after cleavage of a sequence of 20 residues. The mature molecule formed has 79 residues and is processed proteolytically at the N-terminus, yielding the predominant form of 72 amino acids with a molecular weight of about 8383. Structure, sequence and biological properties of IL-8 have been reviewed by Baggiolini M. et al. (Adv. Immunol. 55: 97, 1994).
IL-8 is produced by many cells such as keratinocytes, epithelial cells, synoviocytes and hepatocytes, to name a few. Among peripheral blood leukocytes, monocytes and neutrophils rather than lymphocytes were found to be the major cellular sources of IL-8.
IL-8 exerts many biological activities in vitro and in vivo. IL-8 is well known for its chemotactic activity and its ability to cause degranulation of human neutrophils. Shape change, activation of the motile system and a rise in cytosolic free Ca.sup.2+ are rapidly detected in neutrophils treated with IL-8. The release of vitamin B.sub.12 -binding protein from specific granules was also observed. IL-8 also causes degranulation of the azurophil granules and release of elastase and other hydrolases. Such degranulation is accompanied by the upregulation of a variety of adhesion molecules at the cell membrane. Degranulation also results in the enhanced expression of the complement receptor type I (CR1) and III (CR3). IL-8 is also a chemotactic factor for eosinophils and for human lymphocytes, particularly T cells.
The biological effects of IL-8 are mediated through seven transmembrane domain, G-protein-coupled receptors. Two types of IL-8 receptors have been described and are defined as the type A and type B. IL-8 receptor type A has a high affinity for IL-8 and a low affinity for Gro.alpha.(melanoma growth stimulating activity), whereas type B has high affinity for both cytokines. While among peripheral blood leukocytes, neutrophils strongly express both types of IL-8 receptors, monocytes and CD8.sup.+ T lymphocytes expressed IL-8 receptors to a lower level. No detectable level of IL-8 receptors was found on B cells and CD4.sup.+ T lymphocytes.
There is accumulating evidence in support that IL-8 plays an important role in the inflammatory process of many pathologies; indeed, IL-8 has been detected in inflammatory tissues or exudates such as in psoriatic scale extracts, in synovial fluid from patients with rheumatoid arthritis or gout, in pleural fluid from emphysema patients, and in bronchoalveolar lavages from patients with respiratory distress syndrome. Moreover, antiviral properties have recently been ascribed to the chemokines RANTES and MIP-1.alpha. and .beta., belonging to the C--C chemokine subfamily, which were found to induce inhibition of HIV-1, HIV-2 and SIV replication in vitro
Furthermore, IL-8 has been recently reported to have an antiviral effect (Mackewicz and Levy, 1992 AIDS Research and Human Retrovirus 8: 1039-1050). It was shown that IL-8 can inhibit HIV replication in CD4+ lymphocytes under specific conditions. In fact, IL-8 was found to affect viral replication of naturally infected CD4+ cells but had no effect on acutely infected cells. There are several putative mechanisms of antiviral activity; some may be highly selective as sould be the blockade of the attachment of a specific virus to its target cell. Indeed, Idoxuridine, Vidarabine, Acyclovir and Gangiclovir which are specifically used in the treatment of Herpes virus infection, have no effect on other viruses such as HIV, and thus constitute examples of drugs with selective antiviral activity.
Accordingly, data presented by Mackowicz and Levy in no way make predictable that IL-8 might show antiviral activity against all viruses. The selectivity for specific viruses of most drugs presently used in the treatment of viral infection strongly supports this statement. Therefore, the report of the antiviral effect of IL-8 on HIV does not allow any conclusion on the general antiviral activity of IL-8. To date, there is no other proven report of antiviral activity of IL-8.
Finally, TALMADGE'S PCT application PCT/US95/12099 published Mar. 28, 1996 under the publication number WO 96/09062 describes polypeptide analogs of IL-8 and claims that the analogs can be used for the treatment of pathological conditions such as viral infection, bacterial infection, fungal infections, yeast infection, parasitic infection among others. However, TALMADGE doe not present any data to prove its claim which is based on extrapolation or mere desire for the polypeptide to do so.
It would be highly desirable to provide an antiviral agent with greater efficacy and which would not present the undesirable side effects of the known antiviral agents.